Effects of corn processing and dietary fiber source on feedlot performance, visceral organ weight, diet digestibility, and nitrogen metabolism in lambs

In Exp. 1, early-weaned Targhee and Polypay crossbred lambs (60 ewes and 66 rams; initial BW 24 +/- 1.0 kg) were used in a 2 x 3 factorial experiment to determine the effects of corn processing (whole shelled corn [WSC] or ground and pelleted corn [GC]) in combination with supplemental fiber (none [control]; soybean hulls, SBH [highly digestible]; or peanut hulls, PH [highly indigestible]) on DMI, ADG, feed efficiency, and visceral organ weight. For the total trial, WSC resulted in a 4% increase (P < .01) in ADG vs GC, and supplemental fiber resulted in increased (P < .01) DMI and ADG vs the control diet. Experiment 2 was conducted using 12 Targhee and Polypay crossbred wether lambs (initial BW 25 +/- 7 kg) to determine the effects of corn processing and fiber source in high-concentrate diets on diet digestibility and N retention using the same diets as in Exp. 1. Lambs fed WSC had greater (P < .001) apparent N digestion, true N digestion, and N retention (P < .01) than those fed GC. The apparent digestibilities of DM, OM, and NDF were greater (P < .001) for WSC than for GC diets. Peanut hulls resulted in decreased (P < .01) DM, OM, and NDF apparent digestibilities compared with the control and SBH diets. Starch digestion was not affected (P > .10) by diet. Whole corn resulted in improved DM, OM, NDF, and N digestibility compared with GC. Overall, both the SBH and PH diets resulted in greater DMI and ADG than the control diet, which lacked supplemental fiber.     

Low-quality roughages in high-concentrate pelleted diets for sheep: digestion and metabolism of nitrogen and energy as affected by dietary fiber concentration

Two trials were conducted to evaluate effects of, and interactions between, level and source of fiber in the diet on ruminal environment, microbial protein synthesis, nutrient digestion and flow of digesta through the gastrointestinal tract of multiple-fistulated sheep (trial 1; 4 X 4 Latin square design) and on ruminal, digestive and metabolic characteristics of early-weaned lambs (trial 2; randomized complete block design; 3 periods). All diets tested were pelleted and were formulated to contain either 39% or 25% neutral detergent fiber (NDF), with corncobs or cottonseed hulls (CSH) as the major NDF (roughage) sources. In trial 1, dry-matter (DM) and organic-matter (OM) digestibilities were not different (P greater than .05) among treatments. Digestibility of NDF was higher (P less than .05) with high-fiber. Bacterial N synthesis (g N/kg OM truly digested) was not different (P greater than .05) among treatments. Molar proportion acetate was higher (P less than .05) and molar proportion propionate lower (P less than .05) when sheep were fed high-fiber diets. In trial 2, apparent DM digestibility was higher (P less than .05) for lambs fed diets containing corncobs. Energy digestibility was higher (P less than .05) at the low-fiber level and for lambs fed diets containing corncobs. Apparent NDF digestibility by lambs was higher (P less than .05) at the high-fiber level and for lambs fed diets containing corncobs. Nitrogen retained (percentage of N intake) was higher (P less than .05) for lambs fed diets containing CSH. Ruminal pH and molar proportion acetate were higher (P less than .05) and molar proportion propionate lower (P less than .05) for lambs fed high-fiber diets. Although responses to corncob vs CSH inclusion in high-energy pelleted diets differ, both roughages are effective as fiber sources in sheep diets.     

Effect of roughage particle size on ruminal, digestive and metabolic characteristics of early-weaned lambs fed pelleted corncob-concentrate diets

Two experiments were conducted to determine effects of feeding corncobs of various mean particle size (MPS) on ruminal, digestive and metabolic characteristics of early-weaned lambs fed pelleted 74.9% concentrate:25.1% corncob diets. The MPS of corncobs in diets was 6.5, 5.4, 1.4 and .8 mm, respectively. As particle size decreased, percentage starch decreased and percentage neutral detergent fiber (NDF), acid detergent fiber (ADF) and cellulose increased. In Exp. 1, 28 crossbred rams (seven/treatment, avg initial wt, 15.3 kg) were used in a randomized complete-block design. In Exp. 2, lambs from Exp. 1 were re-weighed (avg initial wt, 16.8 kg) and fed the same diets as in Exp. 1. In Exp. 1 and 2, lambs ingested dry matter (DM) equal to 2.68 and 3.74% of body weight, respectively. In Exp. 1, apparent DM digestibility was unaffected by corncob MPS; however, in Exp. 2, DM digestibility was highest (68.8%) for lambs fed the 6.5-mm diet and lowest (63.8%) for those fed the .8-mm diet. Apparent starch digestibility was high (greater than 98.8%) in both experiments. Neutral detergent fiber and ADF digestibilities were highest for lambs fed the 1.4-mm diet (50.5 and 43.6%, Exp. 1; 39.6 and 28.9%, Exp. 2). A dramatic increase (6.8 to 39.1%) in acid detergent lignin (ADL) digestibility was observed in Exp. 1 as corncob MPS decreased. In Exp. 2, ADL digestibilities were similar for lambs fed the 6.5-, 5.4- or 1.4-mm diets (avg value, 5.9%) and highest for those fed the .8-mm diet (29.7%). Nitrogen metabolism was unaffected by corncob MPS. In Exp. 1, digestible energy intake, corrected for urinary losses, did not differ among treatments but in Exp. 2, lambs consuming the 6.5-mm diet had higher corrected digestibility energy intakes (1,926.6 kcal/d) than did those fed other diets (avg, 1,832.4 kcal/d). Ruminal pH sampled 4 h post-feeding was highest for lambs consuming the 6.5-mm diet (6.25) in Exp. 1 and the 1.4-mm diet (5.89) in Exp. 2. Lowest ruminal pH (5.30 and 5.36, respectively) was for lambs consuming the .8-mm diet in Exp. 1 and the 5.4-mm diet in Exp. 2. Ruminal lactate concentrations were variable within and among treatments. Total ruminal volatile fatty acid (VFA) concentrations were similar across treatments but in Exp. 2, there was a shift in molar proportions from acetate to propionate as corncob MPS decreased.(ABSTRACT TRUNCATED AT 400 WORDS)     

Influence of two levels of enzyme preparation on ruminal fermentation, particulate and fluid passage and cell wall digestion in wether lambs consuming either a 10% or 25% grain diet

Effects of a fungal enzyme preparation on ruminal fermentation, digesta kinetics and cell wall digestion were studied. Either 0, 22 or 25 g/d of enzyme preparation was offered to nine ruminally cannulated Rambouillet or Columbia wether lambs (avg wt 28.6 kg) in two randomized complete block experiments. An alfalfa hay-corn mixture at 2.1% of body weight (10% corn) was used in Exp. 1. In Exp. 2, 2.7% of body weight (25% corn; Exp. 2) was fed. Ruminal samples were collected at 0, 4, 8, 12 and 24 h postfeeding on d 17 of each 22-d period to measure fluid dilution rate and fermentation characteristics. An intraruminal dose of Yb-labeled hay followed by fecal sampling on d 19 through 22 was used to estimate particulate passage and fecal output. Ruminal pH, NH3 concentrations, total volatile fatty acid and proportion of individual acids were not influenced (P greater than .10) by the addition of either level of enzyme preparation in either Exp. 1 or 2. Dry matter digestibility also showed no effect (P greater than .10) of enzyme preparation added to either diet. In Exp. 1, wethers receiving 35 g/d of the enzyme preparation had greater cell wall digestion (49.8%; P less than .05) than wethers receiving either 22 g/d or no enzyme preparation (45.7 and 42.9%, respectively). In Exp. 2, with a 25% corn diet, no influence (P greater than .10) of enzyme preparation was noted on cell wall digestibility. Particulate and ruminal fluid passage rate parameters remained unchanged (P greater than .10) by the addition of either level of enzyme preparation, regardless of the diet fed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of protein concentration and source on nutrient digestibility by mature steers limit-fed high-concentrate diets.

Five ruminally fistulated 3-yr-old mature Holstein steers (average BW 691+/-23 kg) were used in a 5 x 5 Latin square experiment with a 2 x 2 + 1 fact orial arrangement of treatments. Effects of protein concentration and protein source on nutrient digestibility, excretion of DM and fecal N, ruminal fluid volume and dilution rate, ruminal characteristics, and in situ DM disappearance of whole shelled corn, ground corn, and orchardgrass hay were measured in steers limit-fed high-concentrate diets at 1.5% of BW. A negative control basal diet (NC; 9% CP) was supplemented to achieve either 11 or 14% CP; supplemental CP was either from soybean meal (11 and 14% SBM) or a 50:50 ratio of CP from urea and soybean meal (11 and 14% U). Dry matter and OM digestibilities were 5% greater (P < .07) for steers fed the SBM diets than for those fed the U diets. Starch digestibility did not differ (P > .10) among steers fed any of the diets. Nitrogen source did not affect (P > .10) apparent N digestibility or fecal N excretion; however, steers fed the NC diet had the lowest (P < .10) apparent N digestibility compared with those fed all other diets. Ruminal fluid volume was lower (P < .06) when steers were fed the NC diet compared with all other diets; there were no differences (P > .74) among diets for ruminal fluid dilution rate. In general, ruminal ammonia N and VFA molar proportions were not affected by protein source or concentration. Although CP concentration affected (P < .06) in situ DM disappearance of ground corn, CP concentration did not (P > .48) affect total tract digestion of DM or OM. This indicates that CP concentration may have affected site of digestion, but not extent of digestion. When mature ruminants were limit-fed a corn-based diet to meet primarily a maintenance function, protein source and concentration had little effect on measures of nutrient digestion.     

Utilization by sheep of whole shelled corn impregnated with urea, calcium, potassium and sulfur

Twenty-eight growing wether lambs (33.9 kg), adapted to urea for 40 d, were used in a metabolism study to determine if urea impregnation of corn could improve urea utilization. The following diets were compared: 1) whole shelled corn alone, 2) whole shelled corn impregnated with urea, calcium (Ca) as CaCl2, potassium (K) as KC2H3O2, and sulfur (S) as Na2S2O3 X 5H2O, 3) whole shelled corn fed with a dry supplement containing urea, Ca, K and S and 4) whole shelled corn fed with a dry supplement containing soybean meal, Ca and K. Additions were made to provide diets containing 12% crude protein, .37% Ca and .50% K. A 10:1 N (from urea) to S ratio, dry basis was used in urea-containing diets. Corn (90% dry matter) in diet 2 was impregnated by spraying 1.1 liters of an aqueous solution containing the above salts per 10 kg of corn dry matter. After mixing for 10 min in a horizontal mixer, the corn was dried in a laboratory grain drying bin with ambient laboratory air for 48 h. Lambs were fed 350 g of the respective diets plus 35 g orchardgrass hay twice daily during a 20-d metabolism trial. On the last day of the trial, ruminal fluid samples were collected at 0, 1, 2, 3, 4, 5 and 6 h postfeeding and jugular blood was obtained at 0 and 6 h postfeeding. Nitrogen-supplemented diets resulted in increased (P less than .01) absorption and retention of N. Digestibility of dry matter, organic matter and NFE tended to be greater in lambs fed impregnated corn than in lambs fed the other diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of calcium soaps of long-chain fatty acids on feedlot performance, carcass characteristics and ruminal metabolism of steers

Two trials were conducted to determine the effects of calcium soaps of long-chain fatty acids (calcium soap) on feedlot performance, diet digestibility, carcass characteristics and ruminal metabolism of steers fed diets (85% concentrate:15% corn silage) containing 0, 2, 4 or 6% calcium soap. In Trial 1, increasing calcium soap decreased (P less than .05) DM, CP and gross energy intake but increased total fatty acid intake. Feed to gain ratio tended to improve with increased calcium soap; gross energy conversion was not affected (P greater than .05) by diet. Average daily gain and hot carcass weight decreased (P less than .05) with addition of calcium soap; other carcass characteristics were not affected (P greater than .05). Apparent digestibilities of DM, N, energy and ash were not affected (P greater than .05) by calcium soap. Neutral detergent fiber digestibility increased linearly (P less than .08) with increasing calcium soap, whereas digestibility of total fatty acids was affected quadratically (P less than .05); fatty acid digestibility was similar among 0, 2 and 4% calcium soap diets but decreased for the 6% calcium soap diet. In Trial 2, increased calcium soap did not affect (P greater than .05) ruminal VFA concentrations, pH or in sacco NDF disappearance of orchardgrass following 12, 24 and 48 h of incubation. Calcium soap increased (P less than .07) ruminal concentrations of calcium soap fatty acids at 1, 2, 4 and 8 h postfeeding. Calcium soap did not improve performance of feedlot cattle fed high-concentrate diets. Further, calcium soap did not affect ruminal fermentation and did not dissociate significantly even when ruminal pH was below 6 for extended periods of time.     

Synchrony of nutrient supply to the rumen and dietary energy source and their effects on the growth and metabolism of lambs

The objective of the current series of experiments was to assess the effects of dietary synchrony of OM and N supply to the rumen, achieved by altering the sequence of feeding individual ingredients and in diets with different energy sources, on the metabolism and performance of growing lambs. In Exp. 1, the in situ degradability coefficients of OM and N were determined for five feed ingredients and subsequently was used to formulate two diets, based either on barley or sugar beet pulp, to have a similar predicted nutrient content. Within each diet, specific ingredients were shifted between the 0900 and 1600 feeding to provide either a synchronous, intermediate, or asynchronous supply of OM and N to the rumen. In Exp. 2, these diets were fed at a restricted level to 48 growing lambs with an initial live weight of 25.1 +/- 4.22 kg and a slaughter weight of 41.4 +/- 1.94 kg. There was no significant effect of dietary treatment on live weight gain or feed conversion efficiency. Lambs fed the synchronous diets deposited more kidney knob and channel fat than lambs on the asynchronous or intermediate diets (P < 0.05), whereas lambs fed the barley-based diets deposited more carcass (P < 0.05) and noncarcass (P < 0.001) fat than lambs on the sugar beet-based diets. Lambs fed the asynchronous diets retained less energy over the course of the experiment than lambs on the intermediate or synchronous diets (P < 0.05), and had a lower energy efficiency (0.079, 0.097, and 0.093 MJ retained/ MJ of intake, respectively, P < 0.05). Lambs fed the barley-based diets retained more energy than lambs on the sugar beet-based (P < 0.001) and had a higher energy balance (0.095 vs. 0.084 MJ retained/MJ intake, respectively; P < 0.01). Plasma ammonia concentrations mirrored ruminal ammonia concentrations on the barley-based diets, but not sugar beet-based diets. In Exp. 3, lambs fed the sugar beet-based diets had a higher digestibility of OM and NDF (P < 0.001). By contrast, lambs on the barley-based diets had a higher level of purine derivative excretion and microbial N production (P < 0.001). The results indicate that neither dietary synchrony nor energy source significantly influenced growth rate. However, both the asynchronous and sugar beet pulp-based diets resulted in a lower efficiency of dietary energy use, and the avoidance of asynchronous patterns of nutrient release within the rumen can improve energy efficiency in growing lambs.     

Effects of supplemental ruminally degradable protein versus increasing amounts of supplemental ruminally undegradable protein on site and extent of digestion and ruminal characteristics in lambs fed low-quality forage

Four ruminally and duodenally cannulated Suffolk wether lambs (34.5 +/- 2 kg initial BW) were used in a 4 x 4 Latin square designed experiment to compare effects of supplemental ruminally degradable protein (RDP) vs. increasing amounts of supplemental ruminally undegradable protein (RUP) on ruminal characteristics and site and extent of digestion in lambs. Lambs were fed a basal diet of crested wheatgrass hay (4.2% CP) for ad libitum consumption, plus 1 of 4 protein supplements: isolated soy protein (RDP source) fed to meet estimated RDP requirements assuming a microbial efficiency of 11% of TDN (CON) or corn gluten meal (RUP source) fed at 50, 100, or 150% of the supplemental N provided by CON (C50, C100, and C150, respectively). Neither NDF nor ADF intake was affected (P >/= 0.18) by protein degradability, but they increased or tended to increase (P /= 0.26) for CON and C100, but increased (P /= 0.33) by protein degradability. However, true ruminal N digestibility was greater (P = 0.03) for CON compared with C100. Ruminal ammonia concentrations were greater (P = 0.002) for CON compared with C100 lambs, and increased (P = 0.001) with increasing RUP. Microbial N flows were not affected (P >/= 0.12) by protein degradability or increasing RUP. Likewise, neither ruminal urease activity (P >/= 0.11) nor microbial efficiency (P >/= 0.50) were affected by protein degradability or level of RUP. Total tract OM, NDF, and ADF digestibility was greater (P 相似文献   

Effect of dietary protein level on nitrogen metabolism in lambs: studies using 15N-nitrogen

Six wether lambs (31 kg) were randomly assigned to two treatments (three lambs/treatment): a high protein intake (HP; 21 g N/d) or a low protein intake (LP; 12 g N/d). Each lamb received 860 g/d dry matter (DM) of a pelleted diet (75% corn-soybean meal, 25% cottonseed hulls) offered hourly in 24 equal portions. Single injections of 15N-labelled compounds were made into the ruminal NH3-N and blood urea-N pools to measure the rate of flux through, and transfer of N between, these and the bacterial N pool. Total tract digestibilities of DM and N were lower (P less than .05) for the LP than the HP treatment. Abomasal flows of total, feed or bacterial N tended to be greater (P greater than .05) in lambs fed HP than LP. Lambs fed HP excreted more (P less than .01) urinary N, yet retained a greater (P less than .01) amount of N than lambs fed LP (6.2 vs 1.8 and 9.7 vs 4.1 g N/d, respectively). Pool size and production rate for both ruminal NH3-N and blood urea-N were greater (P less than .05) for the HP than LP treatment. Lambs consuming HP degraded more (P less than .05) blood urea-N in the gastro-intestinal tract (13.4 vs 6.9 g N/d); however, lambs fed LP degraded a greater (P less than .05) percentage of synthesized body urea-N (88.7 vs 71.8%). Ruminal NH3-N absorption was greater (P less than .01) for the HP than LP treatment (3.1 vs .5 g N/d). Although the percentage of bacterial N derived from ruminal NH3-N was similar (P greater than .05) between diets (51.1 vs 63.9), a greater (P less than .05) percentage of bacterial N was derived from blood urea-N in lambs fed LP than HP (77.1 vs 30.2%). Lambs fed LP incorporated a greater (P less than .10) amount of blood urea-N into bacterial N than lambs fed HP (5.5 vs 2.6 g N/d). These data are interpreted to suggest that blood urea-N may provide a substantial quantity of N for bacterial protein synthesis and, thus, may be an important source of protein in the deficient animal. In addition, urea recycling may play an important role in the recovery of ruminal NH3-N lost through absorption in animals fed a high level of protein.     

Influence of breed and diet on growth, nutrient digestibility, body composition and plasma hormones of Brangus and Angus steers

Two split-plot designed experiments were conducted to determine the effects of breed (Angus, A, or Brangus, B) and diet (fescue hay, FH; corn silage, CS; or concentrate) on composition and rate of growth, diet digestibility and plasma hormones of steers. In Exp. 1, 10 steers (five of each breed) were fed a CS-based diet followed by a FH-based diet for two consecutive 60-d periods. Both breeds had lower (P less than .01) DM intake and digestibility when fed FH than when fed CS diets. The B steers had higher (P less than .01) plasma insulin concentrations than A steers when fed the CS diet. In Exp. 2, during two consecutive years, 10 steers previously fed CS- and FH-based diets were finished with a corn silage-whole shelled corn-based diet. During yr 1, A steers had higher (P less than .01) DM intake and plasma triiodothyronine (T3) and thyroxine (T4) concentrations (P less than .05) than B steers did. Although final weights were similar (P greater than .10), A steers had heavier (P less than .05) carcass weights than B steers did. During yr 2, A steers had higher (P less than .07) DM and starch digestibilities and higher (P less than .01) plasma T4 concentrations than B steers did. The greater (P less than .01) energetic efficiency of A steers was attributed to the greater rates of fat deposition during yr 2. Regardless of type of diet fed, A steers were more efficient at depositing energy. Higher circulating T4 concentrations of A than B steers may explain some of the physiological differences between these breeds.     

Digestibility and dry matter intake of diets containing alfalfa and kenaf

Two experiments were conducted to determine the dietary value of pellets containing kenaf (Hibiscus cannabinus cv. 'Everglade 41') hay. Averaged across both experiments, kenaf pellets contained 82.6% kenaf hay, 16.6% liquid molasses, and 0.8% mineral oil. The chemical composition of the kenaf pellet was 12.6% crude protein (CP), 41.2% neutral detergent fiber (NDF), and 14.4% acid detergent fiber (ADF). In Exp. 1 (digestion and N balance trial), 18 lambs (body weight [BW] = 36.4 kg) were blocked by BW. Lambs were randomly assigned within a block to Diet 1 (59.5% corn and 40.5% alfalfa pellet), Diet 2 (59.7% corn, 28.4% alfalfa pellets, and 11.9% kenaf pellets), or Diet 3 (59.6% corn, 16.5% alfalfa pellets, and 23.9% kenaf pellets). Diets were formulated so that CP was the first-limiting nutrient. Each diet was limit-fed at 2.4% of BW. Replacing alfalfa pellets with kenaf pellets tended to decrease (P = 0.10) CP and ADF intakes, but increased (P = 0.01) DM digestibility. Diet had no effect (P = 0.33) on N balance. In Exp. 2 (dry matter [DM] intake trial), 32 lambs (BW = 30.4 kg) were blocked by gender and BW. Within a block, lambs were randomly assigned to one of four diets in a 2 x 2 factorial arrangement. Main effects were hay (bermudagrass or fescue) and supplemental protein source (kenaf or alfalfa pellets). Lambs were housed in individual pens with ad libitum access to the assigned hay. Supplemental protein was fed (185 g of DM) once daily. Hay intake was measured weekly for 8 wk. Lambs consumed more (P = 0.002) fescue than bermudagrass hay (743 vs 621 g/ d). Lambs fed fescue hay gained weight more rapidly (P = 0.001) than lambs fed bermudagrass hay (120 vs 72 g/d). Hay intake and ADG were similar (P = 0.90) for lambs fed alfalfa or kenaf pellets. Kenaf hay mixed with molasses and mineral oil can be formed into a pellet. In the diets used in this experiments, kenaf pellets can replace alfalfa pellets in diets fed to lambs without altering forage intake, gain, or N retention.     

Effects of feeding growing cattle high-concentrate diets at a restricted intake on feedlot performance

Three trials were conducted to compare effects of restricted intake of high-concentrate diets vs ad libitum intake of corn silage diets during the growing phase on feedlot cattle performance. In Trial 1, 120 steers (initial BW, 246 kg) were fed 1) a corn silage-based diet ad libitum, 2) a high-moisture corn-corn silage-based diet with intake restricted to a level 20% less than that of the corn silage diet or 3) a high-moisture corn-based diet with intake restricted to a level 30% less than that of the corn silage diet. Steers fed the 20% restricted corn-corn silage-based diet tended (P = .07) to gain slower than those fed the corn silage or 30% restricted high-concentrate diet. Feed efficiency and diet digestibility were greatest for steers fed the 30% restricted-intake, high-concentrate diet (P less than .01). Performance of steers during the subsequent 118-d finishing period was not affected (P greater than .65) by source of energy during the growing period. In Trial 2, ADG of steers fed the 30% intake-restricted, high-concentrate diet was lower (P less than .01) than that of steers with ad libitum access to corn silage. During the 84-d growing period, steers fed supplemental blood meal had 8.3% greater gains and a 6% greater efficiency of feed use than those fed supplemental soybean meal (P less than .01). Monensin did not affect (P = .82) performance of steers fed 30% restricted-intake diets. During the 76-d finishing period, gains and feed conversion were improved (P less than .01) for steers fed the restricted-intake diet in the growing period compared with those given ad libitum access to corn silage. During the growing period in Trial 3, ADG of steers restricted-fed an all-concentrate diet were slightly greater (P less than .10) than ADG of those given ad libitum access to corn silage. Gains did not differ (P = .37) during the subsequent finishing period when steers were switched to 85 or 100% concentrate diets. We concluded that intake of all concentrate diets can be restricted to achieve gains equal to those of steers given ad libitum access to corn silage-based diets without detrimental effects on finishing performance.     

Effects of diet forage:concentrate ratio and metabolizable energy intake on visceral organ growth and in vitro oxidative capacity of gut tissues in sheep

We used 28 crossbred wether lambs to determine the effects of dietary forage:concentrate ratio and metabolizable energy intake on visceral organ growth and oxidative capacity of gut tissues in lambs. Lambs were assigned randomly to a factorial arrangement of dietary treatments consisting of pelleted diets containing either 75% orchardgrass or 75% concentrate fed once daily at either .099 or .181 Mcal ME x (kg BW(.75))(-1) x d(-1). After a 52-d feeding period, lambs were slaughtered to obtain measurements of visceral organ mass and composition and oxidative capacity of isolated epithelial cells. Lamb performance, as measured by DMI, ADG, and efficiency of gain, was greater (P = .0001) for both diets at high ME intake. Likewise, lambs fed 75% concentrate gained faster and more (P < or = .01) efficiently than lambs fed 75% forage. Total digestive tract (TDT; includes rumen, reticulum, omasum, abomasum, and intestines) weight increased (P = .0001) with ME intake and was greater (P = .03) in lambs fed 75% forage than in those fed 75% concentrate. As a percentage of empty body weight (EBW), TDT weight increased with ME intake in lambs fed 75% forage, but it was unaffected by ME intake in lambs fed 75% concentrate (diet x intake, P = .03). Liver weight increased (P = .0001) with ME intake and was greater (P = .005) in lambs fed 75% concentrate vs 75% forage; however, liver weight as a percentage of EBW was increased (P = .0002) with ME intake but was unaffected by diet. Greater ME intake increased (P < or = .02) small intestinal (SI) epithelial and muscle mass of 15-cm sections, whereas jejunal epithelial mass was greater (P = .01) for lambs fed 75% forage vs 75% concentrate. Rumen epithelial concentrations of DNA and RNA increased (P < or = .02) with greater ME intake, whereas SI concentrations of DNA and RNA were largely unaffected by diet or ME intake. The activity of Na(+)-K(+)-ATPase increased in ileal epithelium (P < or = .02) with ME intake and concentrate in the diet, but activity in ruminal epithelium increased (P = .05) with concentrate. Total oxygen consumption by isolated ruminal and intestinal epithelial cells was unaffected by treatment. These data suggest that ME intake and level of dietary forage affect ruminal and intestinal growth via changes in cellular hyperplasia. Additionally, this study supports the concept that ME intake and diet composition alter gut energy expenditure, at least in part, through changes in mass rather than mass specific metabolism.     

Effects of dietary phosphorus, soil ingestion and dietary intake level on performance, phosphorus utilization and serum and alimentary tract mineral concentrations in lambs

Two experiments were conducted with lambs fed concentrate-based diets to study the effects of dietary P and soil ingestion on performance, P utilization and mineral composition of serum and alimentary tract contents. In Exp. 1, 20 wether lambs were fed diets for 21 d in a 2 X 2 factorial arrangement of treatments with .2 or .3% total dietary P and O or 9% added Florida Ultisol (highly weathered soil with high P-fixation capacity) containing 4,600 and 6,400 mg/kg total Al and Fe, respectively. True P absorption increased (P less than .05) from 30 to 42% and from 37 to 54% when soil was added to the basal and high P diets, respectively. In Exp. 2, 24 wether lambs were assigned randomly to a 2 X 2 X 2 factorial arrangement of treatments. Lambs were fed during a 70-d period using diets described previously on either a restricted or an ad libitum basis. Soil increased Fe concentration in ruminal fluid (P less than .05) and ash percentage (P less than .001) in ruminal solids and feces. Aluminum concentration in ruminal solids and feces and Fe in ruminal solids were increased (P less than .001) by soil addition, whereas concentrations of Ca, Mg, P, Zn, Cu and Mn in ruminal solids and feces were decreased (P less than .01) by soil addition. There were time X P interactions on serum inorganic P (P less than .01) and Mg (P less than .05) concentrations. Although high in P-fixing capacity, soil fed to lambs in these experiments improved P utilization. Lambs appeared to be able to adapt to changes in intake of dietary minerals in soil, possibly through adaptation of ruminal microflora or a redistribution of body mineral pools.     

Comparison of the effects of three methods of harvesting and storing alfalfa on nutrient digestibility by lambs and feedlot performance of steers

Two lamb digestion and three steer growth experiments were conducted to study the feeding value of alfalfa harvested as direct-cut silage (DCS) with grain added prior to ensiling or as low-moisture silage (LMS) or hay with grain added at feeding. In all experiments, alfalfa-grain mixtures contained approximately 50% alfalfa and 50% concentrate (dry matter [DM] basis). In Exp. 1, lambs fed DCS alone consumed less DM than lambs fed LMS or hay alone or any of the alfalfa-grain mixtures. Apparent digestibilities of DM and fiber components were higher (P less than .05) for DCS than for LMS or hay. Lambs that were fed LMS digested more (P less than .05) DM and fiber components than lambs fed hay. Addition of grain resulted in increased (P less than .05) DM digestibility and decreased (P less than .05) digestibilities of neutral detergent fiber and acid detergent fiber. In Exp. 2, growing steers (271 kg) fed DCS-grain had increased (P less than .05) weight gains compared with steers fed hay-grain. Steers fed any of the alfalfa-grain mixtures gained weight more rapidly (P less than .05) than steers fed corn silage (CS)-based diets. In a third experiment, finishing steers (283 kg) fed DCS-grain, LMS-grain, hay-grain or CS-based diets performed similarly (P greater than .05), although steers fed DCS-grain had higher (P less than .05) dressing percentages and yield grades than steers that were fed the other three diets and were fatter (P less than .05) than those fed LMS-grain or CS. In Exp. 4, lambs fed DCS-grain or LMS-grain had higher (P less than .05) apparent DM and organic matter digestibilities than lambs fed CS-based diets with similar forage:grain proportions. In Exp. 5, finishing steers (326 kg) fed DCS-grain gained similarly (P greater than .05) to steers fed LMS-grain or an 85% concentrate diet based on high-moisture corn. Steers fed CS diets had lower (P less than .05) gains and increased (P less than .05) feed per gain compared with steers fed DCS-grain, LMS-grain or high-moisture corn.     

Effects of diet and Aspergillus oryzae extract or Saccharomyces cervisiae on growth and carcass characteristics of lambs and steers fed to meet requirements of natural markets

Two studies were conducted to determine the effects of diet and feed additive on growth and carcass characteristics of lambs and cattle destined for all natural markets. In Exp. 1, 48 Dorset × Hampshire lambs (initial BW 29.4 ± 0.1 kg) were used in a randomized complete block experiment to determine the effects of Aspergillus oryzae extract, Amaferm (AMF) supplementation (1 g/d) in an 85% concentrate diet on growth and carcass characteristics. Lambs were allotted to 12 pens (4 lambs per pen), and blocked by sex and BW. Lambs were fed until the average BW of each pen reached a target BW (55.4 kg for wethers and 50.0 kg for ewes), at which time the entire pen of lambs was slaughtered. Amaferm resulted in a greater (P=0.07) G:F. In Exp. 2, 168 crossbred steers (initial BW 300 ± 0.7 kg) were used in a trial with a 3 × 2 factorial arrangement of treatments to examine the effects of 0.5 g/d of Saccaromyces cervisiae boulardii CNCM 1079-Levucell SB (LEV), or 3 g/d of AMF with 2 corn sources, dry whole-shelled corn or high moisture corn, on growth and carcass characteristics. Neither LEV nor AMF improved (P>0.10) carcass characteristics compared with control or non-feed-supplemented steers. Addition of LEV to high-concentrate, corn-based diets did not improve (P>0.10) growth performance of feedlot steers. However, addition of AMF to a diet composed of dry whole-shelled corn resulted in an improvement (P<0.05) in G:F (0.208 vs. 0.194). Results indicate that at the amounts fed, AMF may improve G:F for lambs and steers fed dry corn-based finishing diets.     

Influence of decoquinate on ruminal fermentation, diet digestibility and cattle performance

Three experiments utilizing three Holstein steers (235 and 299 kg avg body weight for Exp. 1 and 2, respectively) were conducted to evaluate the effects of decoquinate, a synthetic coccidiostat, on ruminal fermentation, diet digestibility and performance of steers fed a finishing diet containing monensin and tylosin. Experiment 1 utilized a 70% forage diet, whereas Exp. 2 utilized a 20% forage diet. Each experiment was a 3 X 3 Latin-square design with treatments being 0, .5 and 5 mg decoquinate/kg body weight. Ruminal fermentation characteristics, water kinetics and blood constituents were measured on d 11 of each period, and zero-time volatile fatty acid (VFA) production was measured at 3 and 6 h post-feeding on d 12 to 14. No changes were seen in plasma glucose or L-lactate, ruminal pH, NH3-N or ruminal L-lactate for either experiment. Dry matter digestibility was depressed (P less than .05) at the .5- and 5-mg levels of decoquinate in Exp. 1, but dry matter digestibility was not affected in Exp. 2. No changes were seen in ruminal volume, outflow or total VFA concentration for either experiment. Molar proportions of VFA were not affected in Exp. 1, but the proportions of isobutyrate and butyrate decreased (P less than .05) at the 5-mg level of decoquinate in Exp. 2. Volatile fatty acid production was not changed in Exp. 1, but butyrate production was decreased (P less than .05) at the 5-mg level in Exp. 2. Experiment 3 involved 135 crossbred steers (259 kg avg initial wt), which were stratified by weight into 12 pens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ruminal ciliated protozoa in cattle fed finishing diets with or without supplemental fat

Ruminal samples were collected at slaughter from 364 unfasted steers fed different finishing diets to obtain information on numbers and species distribution of ciliated protozoa in feedlot cattle. Total numbers of protozoa averaged 1.59 X 10(5)/g of ruminal contents. A total of 47 steers (12.9%) were defaunated, but 4.1% of the steers possessed numbers of protozoa greater than 10(6)/g. Entodinium species did not always dominate the protozoan populations; 41 faunated steers (11.2%) were devoid of entodinia, and 79 additional steers (21.7%) possessed populations dominated (greater than 50%) by other genera. Isotricha was the most commonly occurring genus supplanting Entodinium, but Polyplastron and Epidinium were frequently present in high concentrations. Tallow and soybean soapstock supplementation reduced (P less than .05) numbers of protozoa in steers consuming wheat diets. However, yellow grease supplementation did not affect numbers of protozoa in steers fed either sorghum or corn diets. Average ruminal pH was 6.20 on the wheat diet, 6.05 on the corn diet, and 5.69 and 6.23 for the two sorghum diets, respectively. We found no correlation between ruminal pH and numbers of protozoa on any diet. The presence of relatively high protozoan concentrations and few defaunated animals in feedlot cattle necessitates reevaluation of the role that ciliated protozoa play in ruminal metabolism of animals fed processed, high-concentrate diets.     

In vitro effect of pH variations on rumen fermentation, and in vivo effects of buffers in lambs before and after adaptation to high concentrate diets

An in vitro wheat fermentation study (Exp. 1) was conducted to investigate the effect of pH (pH 7, 6, 5 and 4) on rumen lactate and VFA production. In another study (Exp. 2), lambs were fed high concentrate diets containing either no additions (control), 2% sodium bentonite, 2% limestone, 2% NaHCO3 or 10% alfalfa hay. The effect of these diets was determined on ruminal and systemic measurements before and after dietary adaptation. Effect of the control, bentonite, limestone and NaHCO3 treatments on nutrient digestibilities and mineral retentions after adaptation were also determined. Lactate production in the rumen fluid incubated at pH 7 or 6 was negligible. Reducing incubation pH from 6 to 5 resulted in accumulation of both total and L(+)-lactate, but further reduction to pH 4 did not result in an additional increase in lactate production. Variations in incubation pH or time did not affect the ratio of D to L isomers. Lowering the incubation pH to below 6 reduced total VFA production and increased the acetate to propionate ratio. In Exp. 2, the feeding of buffers or alfalfa hay was effective in maintaining a more normal feed intake and ruminal pH, and reduced ruminal lactate. Blood measurements were not affected by dietary treatment. When animals were adapted to the experimental diets, the dietary buffers did not influence rumen and blood measurements. Lambs fed 2% NaHCO3 digested more (P less than .05) organic matter, crude protein, N-free extract and starch, and 2% limestone increased (P less than .05) fiber digestibility. Dietary buffers tended to increase fecal pH and reduce fecal starch Magnesium retention with 2% bentonite, Ca retention with 2% limestone and Na and Mg retention with NaHCO3 were all increased (P less than .05).